Front side illuminated image sensor device structure and method for forming the same

ABSTRACT

An FSI image sensor device structure is provided. The FSI image sensor device structure includes a pixel region formed in a substrate and a storage region formed in the substrate and adjacent to the pixel region. The FSI image sensor device structure includes a storage gate structure formed over the storage region, and the storage gate structure includes a top surface and sidewall surfaces. The FSI image sensor device structure includes a metal shield structure formed on the storage gate structure, and the top surface and the sidewall surfaces of the storage gate structure are covered by the metal shield structure.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/478,664, filed on Mar. 30, 2017, and entitled “Front side illuminatedimage sensor device structure and method for forming the same”, theentirety of which is incorporated by reference herein.

BACKGROUND

Semiconductor devices are used in a variety of electronic applications,such as personal computers, cell phones, digital cameras, and otherelectronic equipment. Semiconductor devices are typically fabricated bysequentially depositing insulating or dielectric layers, conductivelayers, and semiconductive layers of material over a semiconductorsubstrate, and patterning the various material layers using lithographyto form circuit components and elements thereon. Many integratedcircuits are typically manufactured on a single semiconductor wafer, andindividual dies on the wafer are singulated by sawing between theintegrated circuits along a scribe line. The individual dies aretypically packaged separately, in multi-chip modules, for example, or inother types of packaging.

An image sensor is used to convert an optical image focused on the imagesensor into an electrical signal. The image sensor includes an array oflight-detecting elements, such as photodiodes, and a light-detectingelement is configured to produce an electrical signal corresponding tothe intensity of light impinging on the light-detecting element. Theelectrical signal is used to display a corresponding image on a monitoror provide information about the optical image.

Although existing image sensor device structures and methods for formingthe same have generally been adequate for their intended purpose theyhave not been entirely satisfactory in all respects.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It shouldbe noted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIGS. 1A-1H show cross-sectional representations of various stages offorming a FSI image sensor device structure, in accordance with someembodiments of the disclosure.

FIG. 2 shows an enlarged cross-sectional representation of a region A ofFIG. 1E, in accordance with some embodiments of the disclosure.

FIG. 3 shows a top-view of the region A of FIG. 1E, in accordance withsome embodiments of the disclosure.

FIG. 4 shows a cross-sectional representation of a FSI image sensordevice structure, in accordance with some embodiments of the disclosure.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the subject matterprovided. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Some variations of the embodiments are described. Throughout the variousviews and illustrative embodiments, like reference numbers are used todesignate like elements. It should be understood that additionaloperations can be provided before, during, and after the method, andsome of the operations described can be replaced or eliminated for otherembodiments of the method.

Embodiments for a front side illuminated (FSI) image sensor devicestructure and method for forming the same are provided. FIGS. 1A-1H showcross-sectional representations of various stages of forming a FSI imagesensor device structure 100, in accordance with some embodiments of thedisclosure. The FSI image sensor device structure 100 includes a pixelregion, a storage region and a storage gate structure formed on thestorage region. A metal shield structure covers a top surface andsidewall surfaces of the storage gate structure to prevent unwantedstray light from entering the storage gate structure and/or the storageregion.

Referring to FIG. 1A, a substrate 102 is provided. The substrate 102 maybe made of silicon or other semiconductor materials. In someembodiments, the substrate 102 is a wafer. Alternatively oradditionally, the substrate 102 may include other elementarysemiconductor materials such as germanium. In some embodiments, thesubstrate 102 is made of a compound semiconductor or alloysemiconductor, such as silicon carbide, gallium arsenic, indiumarsenide, or indium phosphide, silicon germanium, silicon germaniumcarbide, gallium arsenic phosphide, or gallium indium phosphide. In someembodiments, the substrate 102 includes an epitaxial layer. For example,the substrate 102 has an epitaxial layer overlying a bulk semiconductor.

A pixel region 104 is formed in the substrate 102. The pixel region 104may include photosensitive elements. The photosensitive elements mayinclude a photodiode, a partially pinned photodiode, a pinnedphotodiode, or a photocapacitor. The pixel region 104 may be a dopedregion doped with n-type and/or p-type dopants. The pixel region 104 maybe formed by an ion implantation process, a diffusion process or anotherapplicable process.

A storage region 106 is adjacent to the pixel region 104. The storageregion 106 is configured to temporarily store a charge. The storageregion 106 should not be exposed to incoming light. The storage region106 may be a doped region doped with n-type and/or p-type dopants. Thestorage region 106 may be formed by an ion implantation process, adiffusion process or another applicable process.

A floating node region 108 is adjacent to the storage region 106. Thefloating node region 108 is between the storage region 106 and a dopedregion 110. The floating node region 108 may be a doped region dopedwith n-type and/or p-type dopants. The floating node region 108 may beformed by an ion implantation process, a diffusion process or anotherapplicable process.

The doped region 110 is adjacent to the floating node region 108. Thedoped region 110 may be a doped region doped with n-type and/or p-typedopants. The doped region 110 may be formed by an ion implantationprocess, a diffusion process or another applicable process.

An isolation structure 112 is formed in the substrate 102. The isolationstructure 112 may define and isolate various integrated circuit devices.The isolation structure 112 may be shallow trench isolation (STI)structures or local oxidation of silicon (LOCOS) structures. In someembodiments, the isolation structure 112 is formed in the well region(not shown).

Afterwards, as shown in FIG. 1B, a number of gate structure including afirst gate structure 120, a second gate structure 130, a third gatestructure 140, and a fourth gate structure 150 are formed on thesubstrate 102, in accordance with some embodiments of the disclosure.Each of the gate structure 120, 130, 140, 150 has a respective functionto operate the image sensor device structure. In some embodiments, thefirst gate structure 120 is a transfer gate structure, the second gatestructure 130 is the storage gate structure, and the third gatestructure 140 is transfer gate structure and the fourth gate structure140 is the reset gate structure. In some embodiments, the first gatestructure 120 is the transfer gate structure and it between the pixelregion 104 and the storage region 106. The transfer gate structure 120controls the flow of electrons from the pixel region 104 to the storageregion 106. In some embodiments, the second gate structure 130 is thestorage gate structure and it controls the flow of electrons from thestorage region 106 to the floating node 108.

The first gate structure 120 includes a first gate dielectric layer 122and a first gate electrode layer 124. A pair of first gate spacer layers126 are formed on sidewall surfaces of the first gate structure 120. Thefirst gate dielectric layer 122 may be a single layer or multiplelayers. The first gate dielectric layer 122 may be made of silicon oxide(SiOx), silicon nitride (SixNy), silicon oxynitride (SiON), dielectricmaterial(s) with high dielectric constant (high-k), or a combinationthereof. In some embodiments, the first gate dielectric layer 122 isformed by a deposition process, such as a chemical vapor deposition(CVD) process, a plasma enhanced chemical vapor deposition (PECVD)process, a spin coating process or another applicable process.

The first gate electrode layer 124 may be made of conductive material,such as aluminum (Al), copper (Cu), tungsten (W), titanium (Ti),tantalum (Ta), or another applicable material. The first gate electrodelayer 124 may be formed by a deposition process, such as chemical vapordeposition (CVD), physical vapor deposition (PVD), atomic layerdeposition (ALD), or another applicable process.

The first gate spacer layers 126 may be made of silicon oxide, siliconnitride, silicon oxynitride or another applicable material. In someembodiments, the first gate spacer layers 126 are formed by a chemicalvapor deposition (CVD) process, a physical vapor deposition (PVD)process, or another applicable process.

The second gate structure 130 includes a second gate dielectric layer132 and a second gate electrode layer 134. A pair of second gate spacerlayers 136 are formed on the sidewall surfaces of the second gatestructure 130. The third gate structure 140 includes a third gatedielectric layer 142 and a third gate electrode layer 144. A pair ofthird gate spacer layers 146 are formed on the sidewall surfaces of thethird gate structure 140. The fourth gate structure 150 includes afourth gate dielectric layer 152 and a fourth gate electrode layer 154.A pair of fourth gate spacer layers 156 are formed on the sidewallsurfaces of the fourth gate structure 130.

The second gate dielectric layer 132, the third gate dielectric layer142 and the fourth gate dielectric layer 152 may be independently madeof silicon oxide (SiOx), silicon nitride (SixNy), silicon oxynitride(SiON), dielectric material(s) with high dielectric constant (high-k),or a combination thereof. The second gate electrode layer 134, the thirdgate electrode layer 144, and the fourth gate electrode layer 154 may beindependently made of conductive material, such as aluminum (Al), copper(Cu), tungsten (W), titanium (Ti), tantalum (Ta), or another applicablematerial. The second gate spacer layers 136, the third gate spacerlayers 146 and the fourth gate spacer layers 156 may be independentlymade of silicon oxide, silicon nitride, silicon oxynitride or anotherapplicable material.

Afterwards, an etching stop layer 160 is formed on the first gatestructure 120, the second gate structure 130, the third gate structure140, and the fourth gate structure 150, and on the substrate 102. Insome embodiments, the etching stop layer 160 is made of silicon oxide(SiOx), silicon carbide (SiC), silicon nitride (SixNy), siliconcarbonitride (SiCN), silicon oxycarbide (SiOC), silicon oxycarbonnitride (SiOCN), or another applicable material.

Afterwards, as shown in FIG. 1C, a conductive material 162 isconformally formed on the first gate structure 120, the second gatestructure 130, the third gate structure 140, the fourth gate structure150, and the substrate 102, in accordance with some embodiments of thedisclosure. The conductive material 162 is configured to form a shieldstructure 164 (shown in FIG. 1E), and therefore the shield structure 164has properties that block or reflect the light and prevent the incominglight from entering the underlying second gate structure 130 (e.g. thestorage gate structure).

In some embodiments, the conductive material 162 is made of metalmaterials, such as tungsten (W), copper (Cu), aluminum (Al), titanium(Ti), tantalum (Ta), nickel (Ni), silver (Ag), gold (Au), indium (In),tin (Sn), or a combination thereof. In some embodiments, the conductivematerial 162 is formed by electro-plating, electroless plating,sputtering, chemical vapor deposition (CVD) or another applicableprocess. Although the shielding effect is increased as the thickness ofthe conductive material 162 is increased, the fabrication time and costwill increase. In some embodiments, the conductive material 162 has athickness in a range from about 120 nm to about 150 nm. If the thicknessof the conductive material 162 is too small, the shielding effect may beinsufficient. If the conductive material 162 is over-deposited, aportion of the conductive material 162 may be wasted. When the thicknessof the conductive material 162 is within the above-mentioned range, theshielding effect is better.

Since the conductive material 162 is conformally formed on the gatestructures 120, 130, 140 and 150, the shape of the conductive material164 follows the shape of the gate structures 120, 130, 140 and 150. Inother words, the conductive material 162 includes a first portion and asecond portion, the first portion is directly on the gate structures120, 130, 140 and 150, and the second portion is directly on thesubstrate 102. The first portion is above or higher than the secondportion, and there is a gap between the first portion and the secondportion. In order to compensate for the gap, a dielectric layer 166 isformed in the gap. As a result, a top surface of the dielectric layer166 is level with a top surface of the first portion of the conductivematerial 164.

In some embodiments, the dielectric layer 166 made of anti-reflectivematerial, such as a bottom anti-reflective coating (BARC). Theanti-reflective material may be made of organic or inorganic materials.The inorganic materials may include silicon nitride, silicon oxynitride,titanium nitride, silicon carbide, or other applicable materials. Theorganic materials may include polyimides, polysulfones or otherapplicable materials.

Afterwards, as shown in FIG. 1D, a hard mask layer 168 is formed overthe dielectric layer 166 and the conductive material 162, in accordancewith some embodiments of the disclosure.

Afterwards, the hard mask layer 168 is patterned by a patterning processto have a patterned hard mask layer 168. The patterning process includesa photolithography process and an etching process. Examples of aphotolithography process include soft baking, mask aligning, exposure,post-exposure baking, developing the photoresist, rinsing and drying(e.g., hard baking). The etching process may be a dry etching or a wetetching process.

As a result, a portion of the conductive material 162 is covered by thepatterned hard mask layer 168. Next, an etching process is performed toremove a portion of the dielectric layer 166 and a portion of theconductive material 164 which are not covered or protected by thepatterned hard mask layer 168. In some embodiments, the etching processincludes multiple etching processes. In some embodiments, the etchingprocess is a dry etching process. Afterwards, the remaining dielectriclayer 166 and the patterned hard mask layer 168 are sequentiallyremoved.

Afterwards, as shown in FIG. 1E, a metal shield structure 164 and aconductive structure 165 adjacent to the metal shield structure 164 areformed, in accordance with some embodiments of the disclosure.

When the FSI image sensor device structure 100 is operated in globalshutter mode, the pixel region 104 is configured to detect the incominglight and the storage region 106 is configured to temporarily store acharge. The second gate structure 130 and the storage region 106 shouldnot be exposed to incoming light. However, unwanted stray light maystrike the second gate structure 130 and/or the storage region 106adjacent to the pixel region 104, and result in undesired crosstalk andreduction in global shutter efficiency.

In order to prevent the light from entering the second gate structure130 and the storage region 1006, the metal shield structure 164 isformed on and covers the top surface and sidewall surface of the secondgate structure 130. More specifically, the second gate structure 130 iscompletely surrounded by the metal shield structure 164. In addition,the metal shield structure 164 at least partially covers the storageregion 106.

Note that if the conductive material 162 is removed by a polishingprocess, such as a chemical mechanical polishing (CMP) process, theuniformity of thickness of the conductive material 162 is poor due tothe loading effect and/or the dishing effect caused by the CMP process.For example, the thickness of the conductive material in the centralregion may be not equal to the thickness of the conductive material inthe peripheral region. If the uniformity of thickness of the metalshield structure 164 is poor, the light blocking effect of the metalshield structure 164 may degrade.

Furthermore, if the conductive material 162 is removed by a chemicalmechanical polishing process (CMP) process, a higher/thicker conductivematerial 162 would be required to compensate for excess materialremoval. In other words, in order to prevent the conductive material 162from being damaged by the CMP process, the conductive structure 162 hasto be over-deposited. However, the over-deposited material of theconductive material 162 constitutes an extra waste of material as itwill be removed by the subsequent CMP process.

The conductive material 164 and the conductive structure 165 of thedisclosure are formed by depositing the conductive material 162 and thenremoving a portion of the conductive material 162 in an etching process.Compared with a shield structure formed by a CMP process, the uniformityof the thickness of the conductive material 164 is better, improving theperformance of the image sensor device structure 100.

FIG. 2 shows an enlarged cross-sectional representation of a region A ofFIG. 1E, in accordance with some embodiments of the disclosure.

As shown in FIG. 2, the metal shield structure 164 has a top portion 164a and a sidewall portion 164 b. The top portion 164 a is on a topsurface of the second gate structure 130 (e.g. the storage gatestructure), and the sidewall portion 164 b is on the sidewall surfacesof the second gate structure 130. The sidewall portion 164 b has atapered width from bottom to top. In other words, the sidewall portion164 b has a width which is gradually tapered from bottom to top. A firstangle α1 is between a top surface of the substrate 102 and a sidewallsurface of the metal shield structure 164 when measured clockwise. Thefirst angle α1 is smaller than 90 degrees due to the metal shieldstructure 164 is formed by the etching process. In some embodiments, thefirst angle α1 is in a range from about 75 degrees to about 88 degrees.

The conductive structure 165 has a top surface with a first width W₁ anda bottom surface with a second width W₂. The first width W₁ is smallerthan the second width W₂. A second angle α2 is between a top surface ofthe substrate 102 and a sidewall surface of the conductive structure 165when measured clockwise. In some embodiments, the second angle α₂ is ina range from about 75 degrees to about 88 degrees.

The metal shield structure 164 has a first height H₁ measured from a topsurface of the substrate 102 to a top surface of the metal shieldstructure 164. The conductive structure 165 has a second height H₂measured from the top surface of the substrate 102 to the top surface ofthe conductive structure 165. The first height H₁ is greater than thesecond height H₂. In addition, the top surface of the second gatestructure 130 is higher than the top surface of the conductive structure165 and lower than the top surface of the metal shield structure 164.

The top portion 164 a of the metal shield structure 164 has a firstthickness T₁ which is measured from a top surface of the etching stoplayer 160 to a top surface of the metal shield structure 164 in avertical direction. In some embodiments, the first thickness T₁ is in arange from about 120 nm to about 150 nm. If the first thickness T₁ istoo small, the shielding effect may be insufficient. If the metal shieldstructure 164 is over-deposited, a portion of the metal shield structure164 may be wasted. When the first thickness T₁ of the top portion 164 aof the metal shield structure 164 is within the above-mentioned range,the shielding effect or the light blocking effect is better.

A bottom surface of the sidewall portion 164 b of the metal shieldstructure 164 has a second thickness T₂ which is measure from an innersidewall to an outer sidewall of the sidewall portion 164 b in ahorizontal direction. In some embodiments, the first thickness T₁ isgreater than the second thickness T₂.

FIG. 3 shows a top-view of the region A of FIG. 1E, in accordance withsome embodiments of the disclosure. FIG. 2 is a cross-sectionalrepresentation taken along the AA′ line of FIG. 3.

A via 167 is formed between the metal shield structure 164 and theconductive structure 165. The via 167 and the conductive structure 165are not in the same horizontal plane. The via 167 is made of conductivematerial, such as metal material. The metal material may be tungsten(W), copper (Cu), aluminum (Al), titanium (Ti), tantalum (Ta), nickel(Ni), silver (Ag), gold (Au), indium (In), tin (Sn), or a combinationthereof. The metal shield structure 164 is electrically connected to theconductive structure 165 through a via 167. If the metal shieldstructure 164 is not electrically connected to the conductive structure165, some charges (such as electrons) may accumulate in the metal shieldstructure 164. The accumulated charges may adversely affect theperformance of the image sensor device structure. By connecting themetal shield structure 164 to the conductive structure 165 through thevia 167, the charges in the metal shield structure 164 may betransferred to the conductive structure 165 through the via 167, and theconductive structure 165 is then grounded.

Afterwards, as shown in FIG. 1F, an inter-layer dielectric (ILD) layer170 is formed over the first gate structure 120, the second gatestructure 130, the third gate structure 140, the fourth gate structure150, the metal shield structure 164 and the conductive structure 165, inaccordance with some embodiments of the disclosure.

The ILD layer 170 may include multilayers made of multiple dielectricmaterials, such as silicon oxide, silicon nitride, silicon oxynitride,tetraethoxysilane (TEOS), phosphosilicate glass (PSG),borophosphosilicate glass (BPSG), low-k dielectric material, and/orother applicable dielectric materials. The ILD layer 170 may be formedby chemical vapor deposition (CVD), physical vapor deposition, (PVD),atomic layer deposition (ALD), spin-on coating, or another applicableprocess.

Afterwards, a contact plug structure 172 is formed in the ILD layer 170.The contact plug structure 172 is formed by removing a portion of theILD layer 170 to form a trench, and then filling a conductive materialinto the trench to form the contact plug structure 172. The contact plugstructure 172 has a top surface with a first width and a bottom surfacewith a second width, and the first width is greater than the secondwidth. The contact plug structure 172 has a width gradually tapered fromthe top surface to the bottom surface.

In some embodiments, the contact plug structure 172 is made of metalmaterials, such as tungsten (W), copper (Cu), aluminum (Al), titanium(Ti), tantalum (Ta), nickel (Ni), silver (Ag), gold (Au), indium (In),tin (Sn) or a combination thereof. In some embodiments, the contact plugstructure 172 is formed by electro-plating, electroless plating,sputtering, chemical vapor deposition (CVD) or another applicableprocess. In some embodiments, the metal shield structure 164 and thecontact plug structure 172 are both made of the same material, such astungsten (W). The tungsten (W) has a better gap filling ability thanother metal materials.

Afterwards, as shown in FIG. 1G, an interconnect structure 180 is formedover the ILD layer 170, in accordance with some embodiments of thedisclosure. The interconnect structure 180 is used to electricallyconnect the signal of the gate structures 120, 130, 140 and 150 toexternal environment.

The interconnect structure 180 includes multiple conductive featuresformed in the dielectric layer 182 (such as inter-metal dielectric,IMD). The dielectric layer 182 includes a multiple dielectric layers.The dielectric layer 182 may include silicon oxide, silicon oxynitride,borosilicate glass (BSG), phosphoric silicate glass (PSG),borophosphosilicate glass (BPSG), fluorinated silicate glass (FSG),low-k material, porous dielectric material, or a combination thereof. Insome embodiments, the dielectric layer 182 is formed by a chemical vapordeposition (CVD) process, a spin-on process, a sputtering process, or acombination thereof.

In some embodiments, the dielectric layer 182 is made of an extremelow-k (ELK) dielectric material with a dielectric constant (k) less thanabout 2.5. With geometric size shrinking as technology nodes advance to30 nm and beyond, ELK dielectric material is used to minimize device RC(time constant, R: resistance, C: capacitance) delay. In someembodiments, ELK dielectric materials include carbon doped siliconoxide, amorphous fluorinated carbon, parylene, benzocyclobutenes (BCB),polytetrafluoroethylene (PTFE) (Teflon), or silicon oxycarbide polymers(SiOC). In some embodiments, ELK dielectric materials include a porousversion of an existing dielectric material, such as hydrogensilsesquioxane (HSQ), porous methyl silsesquioxane (MSQ), porouspolyarylether (PAE), or porous silicon oxide (SiO₂).

The conductive features include a number of conductive lines 184 a, 184b, 184 c and a number of conductive vias 186 a, 186 b, 186 c. Each ofthe conductive lines 184 a, 184 b, 184 c is electrically connected tothe one of the conductive vias 186 a, 186 b, 186 c. The conductive lines184 a, 184 b, 184 c are electrically connected to the contact plugstructure 172.

In some embodiments, the first conductive line 184 a is called a firstmetal layer (M₁), the second conductive line 184 is called a secondmetal layer (M₂), and the third conductive line 184 c is called a thirdmetal layer (M₃).

In some embodiments, the conductive features are made of metalmaterials, such as copper (Cu), aluminum (Al), titanium (Ti), tantalum(Ta), nickel (Ni), silver (Ag), gold (Au), indium (In), tin (Sn) or acombination thereof. In some embodiments, the conductive features areformed by electro-plating, electroless plating, sputtering, chemicalvapor deposition (CVD) or another applicable process.

The conductive lines 184 a, 184 b and 184 c and the conductive vias 186a and 186 b, 186 c illustrated are exemplary, and the actual positioningand configuration of the conductive lines 184 a, 184 b, 184 c and theconductive vias 186 a, 186 b, 186 c may vary according to actualapplication.

Next, as shown in FIG. 1H, a trench (not shown) is formed in thedielectric layer 182 and the ILD layer 170, and then a liner layer 188is formed on the sidewall surfaces and a bottom surface of the trench,in accordance with some embodiments of the disclosure.

Next, a transparent dielectric layer 190 is formed on the liner layer188, and a planarizing process is performed to remove the excess of thetransparent dielectric layer 190 outside of the trench. Therefore, alight pipe 191 is formed by the liner layer 188 and the transparentdielectric layer 190, and light pipe 191 has a planar top surface.

The liner layer 188 is used as a protection layer to isolate thetransparent dielectric layer 190 and the adjacent layers, such asdielectric layers 182 of the interconnect structure 180. In someembodiments, the liner layer 188 is made of dielectric materials, suchas silicon oxide or silicon nitride. In some embodiments, the linerlayer 188 is formed by a deposition process, such as a chemical vapordeposition process (CVD), a physical vapor deposition process (PVD), aspin-on coating process or another applicable process.

The transparent dielectric layer 190 is used to provide a path fortransmitting the light from top to bottom. The transparent dielectriclayer 190 has a refractive index that is higher than the refractiveindex of the dielectric layers 182 of the interconnect structure 180. Insome embodiments, the transparent dielectric layer 190 is made ofsilicon nitride, BPSG (boro-phospho-silicate glass), or anotherapplicable material. In some other embodiments, the transparentdielectric layer 190 is made of polymer material, such as polymethylmethacrylate (PMMA), polycarbonate (PC), epoxy, cellulose acetate,cellulose propionate, other suitable polymer materials, or combinationsthereof. The transparent dielectric layer 190 is formed by a spin-onprocess, a chemical vapor deposition (CVD) process or another applicableprocess.

Afterwards, a color filter layer 192 is formed over the light pipe 191,and a microlens structure 194 is formed over the color filter layer 192.The color filter layer 192 aligned with the pixel region 104 isconfigured to filter visible light and allow light in the specificwavelength to pass through the dielectric layer 182 of the interconnectstructure 180 to the pixel region 104.

The color filter layer 192 may be made of dye-based (or pigment-based)polymer for filtering out a specific frequency band (for example, adesired wavelength of light). In some other embodiments, the colorfilter layer 192 is made of resins or other organic-based materialshaving color pigments.

In some embodiments, the microlens structure 194 has a curved uppersurface. The microlens structure 194 may have different shapes and sizesdepending on the index of refraction of the material used for themicrolens structure 194.

As shown in FIG. 1H, a light 200 is disposed over the microlensstructure 194. The microlens structures 194 direct the light 200 to therespective the color filter layer 192. Then, the light 200 passesthrough the color filter layer 192 to the corresponding pixel region104.

When the light 200 enters into the pixel region 104, the pixel region104 generates electrons proportional to an amount of light falling onthe pixel region 104. The electrons are converted into a voltage signalin the pixel region 042 and further transformed into digital signal. Thestorage region 106 is capable of temporarily storing charges transferredfrom the pixel region 104. The charges are then transferred from thestorage region 106 to the floating node region 108.

In order to prevent the light from entering the second gate structure130, the metal shield structure 164 surrounds the second gate structure130. The metal shield structure 164 performs the function of reflectingthe incident light and preventing stray light from entering the secondgate structure 130. Accordingly, the quantum efficiency of the FSI imagesensor device structure 100 is improved and crosstalk is reduced.Furthermore, the global shutter efficiency of the FSI image sensordevice structure 100 is increased.

FIG. 4 shows a cross-sectional representation of a FSI image sensordevice structure 200, in accordance with some embodiments of thedisclosure. Some processes and materials used to form the FSI imagesensor device structure 200 are similar to, or the same as, those usedto form the FSI image sensor device structure 100 and are not repeatedherein.

The difference between the image sensor device structure 200 in FIG. 4and the image sensor device structure 100 in FIG. 1H is that the storageregion 106 is fully covered by the second gate structure 130 and themetal shield structure 164. More specifically, the outer sidewallsurface of the metal shield structure 164 is aligned with a boundary ofthe storage region 106. The metal shield structure 164 is directlyformed on the storage region 106 to increase the shielding effect forthe storage region 106. The metal shield structure 164 performs thefunction of reflecting the incident light and preventing stray lightfrom entering the storage region 106. Accordingly, the quantumefficiency of the FSI image sensor device structure 200 is improved andcrosstalk is reduced.

Embodiments for forming an FSI image sensor device structure and methodfor formation of the same are provided. The FSI image sensor devicestructure includes a pixel region, and a storage region adjacent to thepixel region. The FSI image sensor device structure further includes astorage gate structure on the storage region and a metal shieldstructure on the storage gate structure. The top surface and thesidewall surfaces of the storage gate structure are completely coveredby the metal shield structure to improve the shielding effect. Inaddition, the metal shield structure is not formed by a CMP process, andthe uniformity of thickness of the metal shield structure is improved.Therefore, the global shutter efficiency is increased and theperformance of the FSI image sensor device structure is improved.

In some embodiments, an FSI image sensor device structure is provided.The FSI image sensor device structure includes a pixel region formed ina substrate and a storage region formed in the substrate and adjacent tothe pixel region. The FSI image sensor device structure includes astorage gate structure formed over the storage region, and the storagegate structure includes a top surface and sidewall surfaces. The FSIimage sensor device structure includes a metal shield structure formedon the storage gate structure, and the top surface and the sidewallsurfaces of the storage gate structure are covered by the metal shieldstructure.

In some embodiments, an FSI image sensor device structure is provided.The FSI image sensor device structure includes a pixel region formed ina substrate and a storage region formed in the substrate and adjacent tothe pixel region. The FSI image sensor device structure includes afloating node region formed in the substrate and adjacent to the storageregion and a metal shield structure formed on the storage region, Themetal shield structure has a first height measured from a top surface ofthe substrate to a top surface of the metal shield structure. The FSIimage sensor device structure also includes a conductive structurebetween the storage region and the floating node region. The conductivestructure has a second height measured from the top surface of thesubstrate to a top surface of the conductive structure, and the metalshield structure is electrically connected to the conductive structureand the second height is smaller than the first height.

In some embodiments, a method for forming an FSI image sensor devicestructure is provided. The method includes forming a pixel region and astorage region in a substrate and forming a storage gate structure onthe storage region. The method includes forming an etching stop layer onthe storage gate structure and on the substrate and forming a conductivematerial on the etching stop layer and the storage gate structure. Themethod further includes removing a portion of the conductive material toform a metal shield structure and a conductive structure. The metalshield structure covers a top surface and sidewall surfaces of thestorage gate structure, and the conductive structure is adjacent to themetal shield structure.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

1. A front side illuminated (FSI) image sensor device structure,comprising: a pixel region formed in a substrate; a storage regionformed in the substrate and adjacent to the pixel region; a storage gatestructure formed over the storage region, wherein the storage gatestructure comprises a top surface and sidewall surfaces; and a metalshield structure formed on the storage gate structure, wherein the topsurface and the sidewall surfaces of the storage gate structure arecovered by the metal shield structure.
 2. The front side illuminated(FSI) image sensor device structure as claimed in claim 1, furthercomprising: a contact etching stop layer between the metal shieldstructure and the storage gate structure, wherein the contact etchingstop layer is in direct contact with the metal shield structure.
 3. Thefront side illuminated (FSI) image sensor device structure as claimed inclaim 1, wherein the metal shield structure comprises a top portion anda sidewall portion, the top portion is on a top surface of the storagegate structure, and the sidewall portion is on sidewall surfaces of thestorage gate structure, the sidewall portion has a tapered width from abottom to a top.
 4. The front side illuminated (FSI) image sensor devicestructure as claimed in claim 1, further comprising: a light pipe formedover the pixel region; a color filter layer formed over the light pipe;and a microlens structure formed over the color filter layer.
 5. Thefront side illuminated (FSI) image sensor device structure as claimed inclaim 1, further comprising: a conductive structure formed on thesubstrate and adjacent to the storage gate structure, wherein theconductive structure is electrically connected to the metal shieldstructure.
 6. The front side illuminated (FSI) image sensor devicestructure as claimed in claim 5, wherein the conductive structure has atop surface with a first width and a bottom surface with a second width,and the second width is greater than the first width.
 7. The front sideilluminated (FSI) image sensor device structure as claimed in claim 5,wherein an angle between a top surface of the substrate and a sidewallsurface of the conductive structure is in a range from about 75 degreesto about 88 degrees when measured clockwise.
 8. The front sideilluminated (FSI) image sensor device structure as claimed in claim 5,further comprising: a floating node region formed in the substrate andadjacent to the storage region, wherein the conductive structure isbetween the floating node region and the storage region.
 9. The frontside illuminated (FSI) image sensor device structure as claimed in claim8, further comprising: a contact plug structure formed on the floatingnode region, wherein the contact plug structure and the metal shieldstructure are both made of the same material.
 10. A front sideilluminated (FSI) image sensor device structure, comprising: a pixelregion formed in a substrate; a storage region formed in the substrateand adjacent to the pixel region; a floating node region formed in thesubstrate and adjacent to the storage region; a metal shield structureformed on the storage region, wherein the metal shield structure has afirst height measured from a top surface of the substrate to a topsurface of the metal shield structure; and a conductive structurebetween the storage region and the floating node region, wherein theconductive structure has a second height measured from the top surfaceof the substrate to a top surface of the conductive structure, the metalshield structure is electrically connected to the conductive structureand the second height is smaller than the first height.
 11. The frontside illuminated (FSI) image sensor device structure as claimed in claim10, further comprising: a storage gate structure formed on the storageregion; and a contact etching stop layer formed on the storage gatestructure, wherein the contact etching stop layer is between the storagegate structure and the metal shield structure.
 12. The front sideilluminated (FSI) image sensor device structure as claimed in claim 11,wherein the metal shield structure has a sidewall portion which isdirectly formed on a sidewall of the storage gate structure, and thesidewall portion has a width which is gradually tapered from a bottom toa top.
 13. The front side illuminated (FSI) image sensor devicestructure as claimed in claim 11, wherein a top surface of the storagegate structure is higher than a top surface of the conductive structureand lower than a top surface of the metal shield structure.
 14. Thefront side illuminated (FSI) image sensor device structure as claimed inclaim 10, further comprising: a light pipe formed on the pixel region; acolor filter layer formed over the light pipe; and a microlens structureover the color filter layer.
 15. The front side illuminated (FSI) imagesensor device structure as claimed in claim 10, wherein an outersidewall surface of the metal shield structure is aligned with aboundary of the storage region.
 16. The front side illuminated (FSI)image sensor device structure as claimed in claim 10, wherein theconductive structure has a width which is gradually tapered from abottom surface to a top surface. 17-20. (canceled)
 21. A front sideilluminated (FSI) image sensor device structure, comprising: a pixelregion formed in a substrate; a storage region formed in the substrateand adjacent to the pixel region; a storage gate structure formed on thestorage region; a metal shield structure formed on the storage gatestructure; and a conductive structure formed on the substrate andadjacent to the storage region, wherein the conductive structure iselectrically connected to the metal shield structure through a via, andthe conductive structure and the pixel region are on opposite sides ofthe storage gate structure.
 22. The front side illuminated (FSI) imagesensor device structure as claimed in claim 21, further comprising: acontact etching stop layer formed on the storage gate structure, whereinthe contact etching stop layer is between the storage gate structure andthe metal shield structure.
 23. The front side illuminated (FSI) imagesensor device structure as claimed in claim 21, wherein the metal shieldstructure has a sidewall portion which is formed on a sidewall of thestorage gate structure, and the sidewall portion has a width which isgradually tapered from a bottom to a top.
 24. The front side illuminated(FSI) image sensor device structure as claimed in claim 21, wherein themetal shield structure has a first height measured from a top surface ofthe substrate to a top surface of the metal shield structure, and theconductive structure has a second height measured from the top surfaceof the substrate to a top surface of the conductive structure, and thesecond height is smaller than the first height.